Thinking to install Agency Power full exhaust with catalytic converters for lower sound and smell. Have few questions:
Is there a space to install cats, probably they are going to be 4" diameter.
What is the best place: right after headers or where original secondary cats were before?
Which in/out diameter should be: 2.75" or 3"?
In other threads were recommendations to put metal one from random technology (RT) or stainless work. Any other good options?

Thanks

Are you talking about the complete with header set and the 200 cell race cats(optional with kit) or re-installing your primary cats downstream from the header collector? If reinstalling primaries down stream that may be a stretch, literally for the 02 sensors and would require some welding work. If you have a kit without cats then random is a great choice....2.75 ideal but running to 3 wouldn't hurt. You could also run additional resonators to cut sound. I doubt it would change the smell much. Smell issue usually comes when you remove the primary cat.

Thanks for the input.
I ordered headers, middle section and cat back from Agency Power, which does not come with cats. Planning to replace Kleeman shorties.
What kind of resonators could be used if AP already has X-pipe? The main part of a resonator is the connection between two banks. Stock resonator has 2 paths - small diameter H pipe and the resonator body, which is connected to both banks through collection of small holes.
I currently have installed two Magnaflow 10416 instead of a resonator. It might not be good to install them with AP because of the 2.5" diameter. I tried before MagnaFlow 11386 with X-pipe as somebody mentioned and did not like it.
It would be better to install cats right after headers, if possible I think